1. Field of the Invention
The present invention relates generally to utility pliers and, more particularly to pliers that self-adjust for grasping a work piece and/or self-locking pliers for automatically locking the pliers into engagement with the work piece.
2. Description of the Prior Art
Many types of handheld utility pliers are known in the art. Conventional pliers typically include two plier members interconnected in a scissor-like arrangement allowing for a work piece to be grasped by jaw portions of the pliers in response to movement of handle portions of the pliers. Over the years, numerous improvements have been made to the conventional plier design in order to obtain a better and more efficient plier. For example, self-adjusting pliers have been developed in order to provide a set of pliers that more easily adjust to the size of a given work piece. In addition, self-locking pliers have been developed in order to provide a set of pliers that will allow the pliers to remain in locking engagement with the work piece.
U.S. Pat. No. 4,651,598 discloses a self-adjusting utility plier. These pliers provide for self-adjustment through employment of a spring-biased control arm positioned between the handles. During the self-adjustment, the pivot point of the pliers lies in the spring-biased control arm. As can be appreciated, the location of the pivot point is continuously changing until such time as the work piece is engaged resulting in the center of the pawl member becoming the main pivot point. A disadvantage of such an arrangement is the lack of controlled, rotating movement inherent in the arrangement of the continuously changing initial pivot point. This produces slack in the pliers which may lead to unpredictable pawl engagement between the pawl member and cooperating rack. Another disadvantage of the compound movement inherent in the control arm linkage and its continuously changing location of the pivot point, as opposed to a simple pivoting movement around a fixed pivot point, is the requirement for generous clearance between the moving parts of the pliers. Consequently, when the teeth of the pawls and the mating teeth come into engagement as a result of clamping force applied to the handles, a different set of teeth may become engaged at different times in essentially identical clamping operations resulting in unpredictable clamping performance. Consequently, excessive slack within the linkage-based mechanism has to be taken up each time an object is grasped and a significant portion of the handle movement is dissipated before clamping forces are being applied to the work piece. This limits the separation of the jaws for a given handle spacing, limiting the size of object that can be grasped. Conversely, to achieve a larger jaw opening for grasping larger objects, the handle spacing becomes excessive for one-handed operation of the pliers. In addition, the main pivot point is located inside of a pawl which is itself inside of an elongated channel or slot. A disadvantage of this arrangement is that this limits how close the main pivot point can be located to the jaws and thus, the ultimate leverage that can applied by squeezing the handles is limited. Similar self-adjusting utility pliers are disclosed in U.S. Pat. Nos. 4,662,252, 4,802,390, 4,893,530, 5,060,543 and 5,351,584.
U.S. Pat. No. 5,140,876 discloses variable-fulcrum pliers. The pliers initially pivot about a fixed pivot pin until the jaws of the pliers grip a solid object. The jaws then become the fulcrum which causes the pivot point to shift to a fixed pivot lug which acts as the fulcrum of the pliers as additional pressure is applied to the handle-portions of the pliers. In this arrangement, the two pivot points are aligned transversely to the longitudinal axis of the pliers. A disadvantage of this arrangement is that there is not rapid self-adjustment with minimum handle movement during the adjustment cycle. A further disadvantage is that by transversely aligning the pivot points with respect to the longitudinal axis of the pliers, the maximum leverage during the clamping cycle is not obtained.
As to self-locking pliers, the most common self-locking plier is the well-known VISE-GRIP pliers. VISE-GRIP pliers employ a toggle mechanism which allows for the jaws to be maintained in locking engagement with a work piece once a force is applied to the handle members of the pliers. Typically, VISE-GRIP pliers include an adjustment screw which must be initially adjusted to set the opening of the jaws in relation to the work piece to be grasped. As can be appreciated, operation of the VISE-GRIP pliers requires several steps and further requires that the user employ both hands to operate the same. Examples of the well-known VISE-GRIP pliers are disclosed in U.S. Pat. Nos. 3,354,759, 3,496,808, 5,056,385 and 5,435,214.
Still other pliers have been developed which include a combination of the self-adjusting and self-locking features. Such pliers are disclosed in, for example, U.S. Pat. Nos. 1,772,428, 1,944,116 and 2,620,697. The pliers disclosed in these patents utilize an arcuate arm positioned between the handle members of the pliers and employ a clutch arrangement or friction arrangement for adjusting and/or locking the pliers as the handle members are moved toward each other. These type pliers do not provide for a wide range of self-adjustment and the mechanisms employed therein are difficult to operate and require both hands of the user to for operation.
There remains a need for improved self-adjusting and/or self-locking handheld utility pliers which provide a greater mechanical advantage than previously known pliers and which can be easily operated by the user, preferably with one hand.
The present invention has met the above-described needs by providing for improved self-adjusting and/or self-locking pliers.
The self-adjusting pliers for grasping a work piece include first and second plier members each including a handle portion, a jaw portion, and an intermediate portion therebetween. First pivot means are provided on the intermediate portions permitting the jaw portions to converge on the work piece and grasp the work piece in response to initial movement of the handle portions toward each other. In addition, second pivot means are provided on the intermediate portions permitting a further grasping force to be applied to the work piece in response to continued movement of the handle portions toward each other. The second pivot means is positioned closer to the jaw portions than the first pivot means. Advantageously, this allows for a greater mechanical advantage to be obtained. The self-adjusting pliers also include a biasing means, such as, for example, a compression spring positioned between the handle portions and secured to the handle portions, for biasing the handle portions away from each other and the jaw portions away from each other.
The first pivot means includes a first pivot pin attached to the intermediate portion of the second plier member and a positioning slot formed in the intermediate portion of the first plier member. The positioning slot has a generally arcuate portion and a shifting slot portion in communication therewith. The first pivot pin is slidably received in the positioning slot.
In a preferred embodiment, the first pivot pin is positioned in the shifting slot portion of the positioning slot during the initial movement of the handle portions toward each other to grasp the work piece. Also, in the preferred embodiment, the second pivot means includes a second pivot pin attached to the intermediate portion of the first plier member and a generally arcuate main rack on the intermediate portion of the second plier member. The generally arcuate main rack has a plurality of notches where the second pivot pin is in engagement with one of the plurality of notches during the continued movement of the handle portions toward each other to apply the further grasping force to the work piece. Advantageously, the generally arcuate main rack allows for the second pivot pin to be in engagement therewith at a location close to the jaw portions of the pliers. This allows for a greater mechanical advantage to be obtained during the continued movement of the handle portions toward each other to apply the further grasping force to the work piece. When the second pivot pin is in engagement with one of the plurality of notches of the generally arcuate main rack and, during the continued movement of the handle portions toward each other to apply the further grasping force to the work piece, the first pivot pin moves from the shifting slot portion of the positioning slot to the generally arcuate portion thereof.
In a further embodiment, the second pivot means includes a translating pawl pivotally secured by a translating pawl pivot pin to the intermediate portion of the first plier member and a generally arcuate translating rack formed on the intermediate portion of the second plier member. The generally arcuate translating rack includes a plurality of first teeth and the translating pawl includes a plurality of second teeth formed on a first side thereof adjacent the generally arcuate translating rack. The plurality of second teeth are in engagement with the plurality of first teeth of the generally arcuate translating rack during the continued movement of the handle portions toward each other to apply the further grasping force to the work piece.
In another embodiment, the second pivot means further includes a stop member and a spring for urging the translating pawl into a concentric relationship with the generally arcuate translating rack. The stop member is preferably formed on the intermediate portion of the first plier member and positioned for contacting a second side of the translating pawl. The spring includes one end connected to the intermediate portion of the first plier member and another end connected to the translating pawl for urging the translating pawl away from the generally arcuate translating rack and into contact with the stop member. Advantageously, this positions the translating pawl concentrically to the translating rack and allows for simultaneous engagement of all teeth of the translating pawl and, therefore, better and more precise engagement between the translating pawl and the generally arcuate translating rack because of the constant concentric relationship therebetween.
In yet another embodiment the second pivot means includes a rachet pawl pivotally secured by a rachet pawl pivot pin to the intermediate portion of the first plier member and a generally arcuate rachet rack formed on the intermediate portion of the second plier member. The generally arcuate rachet rack includes a plurality of first teeth and the rachet pawl includes a plurality of second teeth formed on a portion of a first side thereof adjacent the generally arcuate rachet rack. The plurality of second teeth are in engagement with the plurality of first teeth of the generally arcuate rachet rack during the initial movement of the handle portions toward each other to grasp the work piece and during the continued movement of the handle portions toward each other to apply the further grasping force to the workpiece. In this embodiment, the first pivot means includes a first pivot pin fixedly secured to the intermediate portion of the second plier member and a generally arcuate positioning slot formed in the intermediate portion of the first plier member where the first pivot pin is slidably received in a generally arcuate positioning slot. The second pivot means further includes engagement means for maintaining the plurality of second teeth of the rachet pawl in continuous engagement with the plurality of first teeth of the generally arcuate rachet rack during the initial movement and the continued movement of the handle portions toward each other. By providing for the engagement means, it is not necessary to form the generally arcuate positioning slot so as to include a shifting slot portion, as in previous embodiments described herein.
The engagement means also includes disengagement means for disengaging the plurality of second teeth of the rachet pawl from the plurality of first teeth of the generally arcuate rachet rack to allow the handle portions to move away from each other and the jaw portions to move away from each other.
In yet another embodiment, the second pivot means includes a pawl member pivotally secured by a pawl pivot pin to the intermediate portion of the first plier member and a generally arcuate rack formed on the intermediate portion of the second plier member where the generally arcuate rack includes a plurality of first teeth and the pawl member includes a plurality of second teeth formed on a first side thereof adjacent the generally arcuate rack. The second pivot means also includes a spring means secured to the intermediate portion of the first plier member for urging the pawl member into a generally concentric relationship with the generally arcuate rack during the initial movement of the handle portions toward each other to grasp the workpiece and for urging the plurality of second teeth of the pawl member into engagement with the plurality of first teeth of the generally arcuate rack during the continued movement of the handle portions toward each other to apply the further grasping force to the workpiece. In this embodiment, the pawl member preferably includes a generally flat top surface and the spring means includes a leaf spring secured to the intermediate portion of the first plier member such that the leaf spring is positioned for cooperating with the generally flat surface of the pawl member during the urging of the pawl member into a concentric relationship with the generally arcuate rack. Preferably, the pawl member also includes a second side adjacent the generally flat top surface with the leaf spring being positioned for cooperating with the second side of the pawl member during of the urging of the plurality of second teeth of the pawl member into engagement with the plurality of first teeth of the generally arcuate rack during the continued movement of the handle portions toward each other to apply the further grasping force to the workpiece. In addition, the first side of the pawl member also preferably includes a bearing surface adjacent the plurality of second teeth, the bearing surface being positioned adjacent the generally flat surface of the pawl member. The pawl member may also include a handle for moving the plurality of second teeth of the pawl member into or out of engagement with the plurality of first teeth of the generally arcuate main rack. Advantageously, this allows for the pliers to be easily maintained in a closed position for convenient storage of the pliers.
In a further embodiment, the second pivot means includes a pawl member having a generally triangular slot formed therein and a pawl pivot pin extending through the intermediate portion of the first plier member and the triangular slot to pivotally secure the pawl member to the intermediate portion of the first plier member. Preferably, the generally triangular slot includes a first region, a second region and a third region. The pawl pivot pin is received generally in the first region of the generally triangular slot during the initial movement of the handle portions toward each other. The pawl pivot pin is received generally in the third region of the generally triangular slot during the continued movement of the handle portions toward each other to apply the further grasping force to the workpiece. The pawl pivot pin is received generally in the second region when tip portions of the plurality of first teeth engage a tip portion of the plurality of second teeth.
In accordance with another aspect of the invention, self-locking pliers for grasping a workpiece are also provided. The self-locking pliers include first and second plier members each including a handle portion, a jaw portion and an intermediate portion therebetween. Fixed pivot means are provided on the intermediate portions for interconnecting the first and second plier members and permitting the jaw portions to converge on the workpiece and grasp the workpiece in response to movement of the handle portions toward each other. The self-locking pliers also include self-locking means for automatically locking the jaw portions. The self-locking means comprises cam means on the intermediate portions of the first and second plier members, the cam means including a cam rack pivotable between a first position where the handle portions and the jaw portions are extended away from each other and a second position where the jaw portions are converging towards each other. The cam rack includes a cam pin attached thereto. The self-locking means further comprises a biasing spring connected at one end to the cam rack and at the other end to the second plier member for urging the cam rack toward the first position. The self-locking means further comprises a cam slot formed in the intermediate portion of the first plier member with the cam pin being slidably received in the cam slot. The self-locking means also comprises lock pawl means on the intermediate portion of the second plier member adjacent the cam rack where the lock pawl means includes a lock pawl moveable between a locked position for engagement with the cam rack and an unlocked position for disengagement from the cam rack.
The self-locking pliers may also include clamping means for interacting with the cam means to apply an additional clamping force to the workpiece. The clamping means includes a pump lever pivotally connected to the intermediate portion of the second plier member, and a pump pawl pivotally connected to the pump lever and positioned adjacent the cam rack. The pump lever is structured to cause the pump pawl to engage the cam rack and pivot the cam rack toward the second position to apply the clamping force to the workpiece responsive to actuation of the pump lever. Advantageously, it will be appreciated that the self-locking means and the clamping means of the self-locking pliers may be easily operated by the user. Preferably, the self-locking pliers may be operated by one hand of the user thereby allowing for the user""s other hand to be used for other purposes.
In another embodiment of the self-locking pliers, the self-locking pliers may also include self-adjusting means on the intermediate portions for interconnecting the first and second plier members and permitting the jaw portions to converge on the workpiece and grasp the workpiece in response to movement of the handle portions toward each other. The self-adjusting means further permit a grasping force to be applied to the workpiece in response to continued movement of the handle portions toward each other.
It is, therefore, an object of the present invention to provide self-adjusting pliers for grasping workpieces of different sizes.
It is also an object of the present invention to provide self-adjusting pliers which have enhanced mechanical advantage.
It is a further object of the present invention to provide self-adjusting pliers that can be easily and efficiently operated.
It is yet another object of the present invention to provide self-adjusting pliers that can be operated with one hand.
It is another object of the present invention to provide self-adjusting pliers which include spring means for urging a pawl member of the pliers into a generally concentric relationship with a rack of teeth of the pliers.
It is another object of the present invention to provide self-adjusting pliers where a pawl member of the pliers includes a handle for moving the pawl member into and out of engagement with a rack of teeth of the pliers.
It is also an object of the invention to provide self-adjusting pliers that may easily be maintained in a closed position for storage of the pliers.
It is a further object of the present invention to provide self-adjusting pliers where a pawl member of the pliers includes means for ensuring smooth and proper engagement between the pawl member and rack of teeth of the pliers.
It is yet another object of the present invention to provide self-locking pliers for automatically locking the jaw portions of the pliers into engagement with a workpiece.
Still another object of the invention is to provide self-locking pliers that may be easily and efficiently operated.
It is another object of the invention to provide self-locking pliers that can be operated by the user with one hand.
It is a further object of the present invention to provide self-locking pliers that may apply an additional clamping force to the workpiece following the automatic locking of the jaw portions into engagement with the workpiece.
It is also an object of the present invention to provide pliers having both the capability for grasping the workpiece and for automatically locking the jaw portions into engagement with the workpiece.
It is an object of the present invention to provide pliers such that an unskilled person may operate the pliers in essentially the same manner as conventional pliers.
It is another object to provide locking pliers that are readily releasable from a locked position and easily reset for further operation.
These and other objects of the invention will be more fully understood from the following description of the invention with reference to the drawings appended hereto.